Current wireless communication network solutions, especially those used for indoor networks, include a radio controller which provides power and signaling over an Ethernet cable to and from a radio. This is shown in FIG. 1, where the radio controller (RC) 10 is connected to a backhaul network via a digital baseband unit (DU) 12 via a common public radio interface (CPRI) which may include a fiber connection. The radio controller 10 acts as a power sourcing equipment (PSE) to feed power to the radio device 13 over an Ethernet cable such as CAT 5, 6 or 7 that is ANSI-TIA-EIA 568 compliant. The radio controller 10 also supports communication with the radio device 13 over the Ethernet cable. Power can be delivered on such a cable to a radio unit up to about 200 meters away from the radio controller 10. The radio device 13 is a powered device (PD) that acts as a wireless access point to communicate wirelessly with user equipment (UE) such as mobile phones 11.
There are several common techniques for transmitting power over Ethernet cabling of which two have been standardized under Institute of Electrical and Electronic Engineers (IEEE) specification 802.3af and IEEE 802.3at. FIG. 2 is a schematic of a power sourcing equipment, such as the radio controller 10, which feeds power to, and supports communication with, a powered device, such as the radio device 13. In FIG. 2, power is transmitted on pairs 4/5 and 7/8, while communication such as data and signaling is carried on pairs 1/2 and 3/6. In another embodiment, since only two of the four pairs are needed for communication using IEEE 802.3 10/100 BASE-T, power may be transmitted on the same wiring pairs as the data communication. In this case power may be transmitted on the conductors carrying data and control signals by applying a common-mode voltage to each pair. Because Ethernet uses differential signaling, this does not interfere with data transmission. The common mode voltage is easily extracted using the center tap of the standard Ethernet pulse transformer.
In addition to standardizing existing practice for spare-pair and common-mode data pair power transmission, the IEEE Power over Ethernet (PoE) standards provide for signaling between the PSE and PD. This signaling allows the presence of a conformant device to be detected by the power source, and allows the device and source to negotiate the amount of power required or available.
As noted above, in current solutions, the radio device 13 can only be a maximum distance of about 200 meters from the radio controller 10. The maximum allowed continuous output power per cable in IEEE 802.3af is 15.40 Watt. Specification IEEE 802.3at establishes a 25.50 Watt capability.